1. Field of the Invention
This invention relates to a zoom lens system capable of very close range photography without aggravating its imaging performance.
2. Description of the Prior Art
A system of moving a first lens group toward the object side has heretofore been adopted as the simplest general focusing system of a zoom lens, but if an attempt is made to greatly reduce the photographing close range by this system, aberrations are of course fluctuated and the position whereat the principal ray passing through the center of a diaphragm intersects the first lens group becomes greatly spaced apart from the optical axis and this results in the increased aperture of the foremost lens which in turn provides a great impediment in making the lens system compact, and thus the close range could only be reduced to a certain degree.
Besides this system of moving the first lens group, various methods of imparting to each group a movement different from the movement by the normal zooming to reduce the close range of the zoom lens have been proposed, but these methods are only of such a degree that a movement different from the movement by the normal zooming is imparted to two groups at most, and an attempt to greatly reduce the close range has greatly destroyed to condition of zooming and has therefore greatly aggravated aberrations and thus, most of these methods have suffered from practical problems unless they are used while being considerably stopped down.